Shaped charge bombs comprise a shaped charge warhead section, e.g. of conical or frusto-conical shape, that spreads axially symmetrically from an inner apex or a narrow end to the front end (base) having as a rule the same diameter as the explosive charge. Liners in hollow charge warheads are made of ductile metals such as copper, aluminium, magnesium, tin, zinc, titanium, nickel, iron, zirconium, silver and others, the most commonly used liner metals being copper, certain types of steel and aluminium. Upon detonation of the high explosive charge every liner element (the liner element being a ring cut of the liner) separates when reaching the liner axis of symmetry into two parts or streams, one flowing backwards and forming the slug and the other one bursting forward and forming the jet that penetrates the target. In order to achieve good penetration the jet must have a high tip velocity and a long break-up time and experience has shown that only light and medium weight metals of the kind mentioned hereinbefore meet these requirements.
At the same time it can also be shown that the penetration power of the jet would increase with the density of the liner, which increase, however, is incompatible with the need for a high tip velocity. Thus, for example, while with a copper liner a jet tip velocity of 9.5 km/sec. is achieved, heavy metal jets have tip velocities which are generally below 7 km/sec. The contribution of the fastest part of the jet to the penetration is large and especially important when the shaped charge is used at stand-offs as short as 2-3 charge diameters which are typical to almost all the weapons with shaped charge warheads used today.